The present invention relates to a press-on key switch to be used as the power switch of a compact electronic device such as an electronic clinical thermometer or electronic calculator.
When pressure is applied on the top surface of the key switch device, the movable contact touches the stationary one, and it disconnects when the pressure is released.
FIG. 8 shows a conventional electronic clinical thermometer. A temperature sensor 2, a digital temperature display 3, and a battery storage housing 4 are located at the tip, center, and the rear positions, respectively. A key switch 5 serving as the power switch is provided between the digital display 3 and the battery storage housing 4. As shown by the sectional view of FIG. 9, the key switch surface 5a, on which pressure is applied to activate the key switch 5, is almost flush with the upper surface of a thermometer case 1 due to a rubber spring or flexible part 5b. Whenever the key switch surface 5a is pressed, a movable contact 5c touches a stationary contact 6a on a printed circuit board 6 installed below the movable contact 5c, to alternately turn the power supply on and off. However, since the key switch 5 is activated merely by the depression of the key switch surface 5a, if an operator accidentally presses it sufficiently to turn the power supply off after taking his or her own temperature, the temperature display will be erased. Conversely, an operator may accidentally turn on the power while storing the clinical thermometer in its case and thus, waste the batteries.